The present invention relates to a control device for a throttle valve for use with an internal combustion engine, and more particularly to a throttle valve control mechanism which is suitable for improving the driveability of the vehicle equipped with the engine and the responsive chracteristic of the throttle valve.
A conventional control device for a throttle valve used with an internal combustion engine has such a structure that when the driver depresses the accelerator pedal, the amount by which the pedal is depressed is directly transmitted to the shaft of the throttle valve through a linkage mechanism or a cable provided in the relevant vehicle, thus determining the opening degree of the throttle valve. With a throttle valve controlled by means of such a conventional control device, however, since the opening of the throttle valve and the amount by which the accelerator pedal is depressed by the driver are in such a relationship that the former is directly proportionally determined by the latter, following disadvantages often result: Namely, the pressing force tends to be strong when the driver starts to depress the accelerator pedal, thus causing a sudden increase in the throttle valve opening and accordingly a rapid acceleration; the consequent vibration experienced by the vehicle due to the thrust caused by this rapid acceleration results in a great deterioration of the driveability of the vehicle in the low speed region of the engine. On the other hand, if such an arrangement is made that the throttle valve opening will be small relative to the amount of depression of the accelerator pedal with the intention of improving the driveability in the low speed region, this may result in a deterioration in the responsive characteristic of the throttle valve to the driver's operation of the accelerator pedal in the high speed region of the engine.